bites on tail

Question
Hello,
I have had two female mice living together for 15 months.  One has been having health problems.  Yesterday, I felt a little snag on her tail and thought nothing of it.  Today I looked closer and saw multiple little bites.  Should I go ahead and separate them to protect her, or do you think it's self inflicted?

Answer
Dear Sean,

It's not a cut and dried situation, unfortunately.

The most likely scenario for self-inflicted tail wounds would be that she has mites.  You don't mention what her health problems are; mites can cause symptoms other than itching, such as generally being run down.  If she has mites, the other one does too, and both should be treated.  It is also possible that she is upset and confused, but I would treat for mites.

However, there is the possibility that the other mouse has sensed her weakness and is attacking.  Has there been a lot of squeaking going on?  If so, I would separate the two.

Mice love their companions, so if they do not seem to be fighting I would keep them together, but keep a very close eye out that the problems don't get worse.  If they are fighting they ought to be separated, especially if one is weak and can't defend herself well.

Best of luck to both.

Squeaks,

Natasha